His Promise
by akamagerain
Summary: It's hard enough trying to win back your lost country. Gray didn't need the complication brought on by the feelings his bodyguard gave rise to. Or by the fact that she wanted him dead. A GrayTear Prince-Assassin AU one-shot, with some low-key Nalu.


_**His Promise**_

* * *

It wasn't too hard to see why he had fallen as hard as he had.

He watched silently as she walked to face him, almost regal in her gait, armour almost tailor-made for her – gorgeous but so dangerous at the same time.

He watched as she stood before him, baring her weapon of choice.

Baring it, for him.

* * *

 _'This is good,'_ he thought, as his advisors left his small tent. His eyes darted across the makeshift map they had made. The gaping holes in the new reign's defense were so obvious, it was a wonder no outside force had taken his kingdom.

Then again, no one knew it like he did.

 _'No one alive anyway.'_

Gray immediately screwed his eyes shut against the memories that came flooding back. They always did, but he was never ready.

The fire, the many bodies writhing in agony, the smell of death, the gut wrenching screaming and so, so much blood.

His kingdom had lost so much that night, and it marked the beginning of the darkest age it had ever seen.

Years of tyranny and an awful rule had brought the nation to its knees – crime, death and disease rampant unlike ever before. It hurt Gray even more than his memories, to see what his home had become. Travelling undercover the way he was meant he got to witness so much of it first hand — his country, once one of joy and prosperity despite the cold, now one of distrust, deceit and suffering.

All of which only fuelled his desire to retake his once proud kingdom, and sit in the throne he was born to reign on. Opening his eyes with new resolve, he began mapping his way ahead. So deep in thought was he, that he nearly didn't sense the attack.

At the very last moment, Gray dodged the sword, before quickly turning around, grabbing his attacker by the wrist and folding it to disarm them. He moved confidently, ready to pin her down, but was taken by surprise when his momentum was used against him. Next thing he knew, he was flat on his back, arms immobile under her knees and his own weight, and the blade positioned dangerously across his neck.

Gray could only blink up at his assailant.

She was very obviously beautiful — tall, well built from some obviously very rigorous training, and eyes, oddly familiar, that burned with a hatred he had never seen directed towards him.

"Finally," she breathed, her voice thick with the same rage.

Gray was aware that he could yell, and that even if she did deal a lethal blow she wouldn't be able to get away alive. On second thought however, he realised that she probably didn't mind being killed just then. He didn't like the idea of a life spent trying to kill someone else. And there was another detail too —

"I can tell you've wanted to do this for some time," he managed, steadying his voice. "But I am sorry, I cannot die just yet."

"What?" she seethed.

"I cannot die. You clearly know who I am, and this level emotion wouldn't come from someone who has won against me before. You're clearly my people, and I understand your anger. But I cannot die right now. Too many people's lives are on the line."

He watched as she grit her teeth. She was offended, but also thinking.

Good, she wasn't without a heart.

"And what about those who died?" she asked, sneering at him.

"They died to keep me alive," he said matching her gaze with sincerity. "So, I cannot yet."

"And what about those alive, wishing they were dead? Do you have any idea what you have done?"

Gray's eyes only narrowed.

"Do you have any idea what your people are going through? Just because you abandoned your country and fled like a filthy coward?"

"I do," he said softly.

The honesty in that gaze meant she could see his pain as well.

And he could see how easily she could read it. How much she was struggling to not kill him.

Her grip on her sword loosened, if only a fraction.

"Do you even remember her? Were you there when she…" She was not meeting him eye-to-eye now.

What bothered him was how he knew he should recognise her. And when he understood, he felt far more than just her weight on his chest.

Her voice rang in his head drowning out the sound of his thundering heartbeat, as it had for so, so many nightmares — screaming for him to run to safety.

While she choked on her own lifeblood.

"Ur?" he gasped.

As though burned by the name, she immediately got off of him and braced her sword once more, eyes steely as she watched him sit up slowly, dragging a hand across his face.

"So you do remember." The rage was back. And Gray did not blame her one bit.

"I could never forget," he choked out, looking up at her. She took a step back, because when he did, he was no longer the nineteen-year-old proud warrior prince. No, he was a boy, who had experienced far more than anyone should have at that age.

To her surprise, she found herself feeling for him. She kept a good check on it though, her sword never lowering. She allowed him a moment to gather his thoughts, giving herself the same liberty.

She straightened suddenly, as he stood up and walked close enough for the tip to touch, and cut the hollow of his throat. "I cannot die now," he reiterated, meeting her gaze now evenly, back to being the crown prince, "Not while my kingdom still suffers under that bastard Deliora's reign. I will take back the country and bring her back to her feet. Secure her future. And then," he brought his hand to her blade, holding hard enough for his palm to bleed into the engraving in the steel, "you may take my life. This, I promise you."

He watched her register what he had just done, her eyes wide as she watched him take the highest oath a royal could — one made with their own blood.

"Until that time comes, stay by my side. Do not let me fall by another's blade," he commanded, and she found that she could not turn away from his gaze.

He watched her nod slowly, before pulling away his hand and allowing her to pull back her sword from him.

"I will not bow before you," she promised.

"You will have to," Gray said. "Or you will be a target to those loyal to me. They cannot know of my oath, since now you're not allowed to die either. Not until you've taken what is now yours to take."

Seeing her discomfort with the idea he added, "Though that's only valid for when they're looking."

She lowered her sword, accepting his conditions. He turned around, looking through his trunk and eventually pulling a long cotton cloth to tie around his still bleeding right palm. All the while, leaving his back open to her.

"Summon Erza," he yelled suddenly, startling her.

And within minutes, this Erza strode into the tent.

The next second both women had their swords at each other's neck.

"Both of you, stand down," he said, secretly vowing to never piss either of them off. Well, more than he had before. "Erza, this is…?"

"Ultear."

"…Ultear, my bodyguard."

Erza let her surprise show only for a moment, before arranging her expression back to calm. "So when you finally take heed to my words, you do so with a stranger. I take it you trust this woman?"

Ultear did not miss the way her eyes darted along the blood still on her blade.

"I do. She is Ur's daughter."

Erza stepped back immediately and sheathed her sword, much to Ultear's relief. She could tell that the red-head could have easily posed quite a challenge. She wiped the blood on her sword on her slacks and sheathed it.

"That may in of itself not be a promise of trust," she cautioned Gray, noting his palm. "It bothers me to constantly remind you of this, but please think before hastening into decisions."

"I do, Erza," Gray responded softly.

"Impulsiveness isn't what makes a good prince, let alone a good king. As a matter of fact —"

"Got it, Erza," he whined, running a palm through his hair.

Whined.

At his general.

Ultear took a moment to process that.

"Did you just take that tone with me?" Erza (technically) asked.

"N-no, Ma'am," said Gray palms up and gently backing away.

Puzzling Ultear even more.

"Good," said Erza. She took one last look at his hands and then at Ultear, one that was not particularly friendly. She then turned to step out of the tent. "I will be returning with Lucy shortly. We need to continue charting out our way to the castle," she said.

"I have a good idea of one!" he called after her, clearly excited about his new idea.

Ultear had no clue what to make of anything she had just witnessed. This could definitely not be the famous exiled prince and his loyalists. She had probably trained too hard and passed out again, and was definitely dreaming or something —

"Ultear," he called.

Oh, so he hadn't forgotten her.

"Please stick around for this meeting, you'll need to know the current situation and our plans ahead, I'll fill you in on any questions you may have right after."

"What makes you think that I wouldn't end you right here?"

"You care too much for the people to," he explained, looking at her over his shoulder. "And we're their final hope."

She silently accepted his argument, careful to never seem the least bit friendly or remotely satisfied with their arrangement. She understood why it existed of course, but it put her off anyway.

Why did she have to protect that person she had sworn to kill?

Soon enough, the general was back, with a group of fairly young people in tow. The blonde one she could vaguely recognise, if only because the advisor looked so much like someone from her memory.

The others, she had no clue of — a tall man branded on one side of his face, one awfully fond of metal if his face was anything to go by, a hyperactive one with a cat on his shoulder, an old, clearly irritable lady and…a little girl.

This was the Prince's answer to Deliora and his massive army?

Ultear wondered — not for the last time — if she would even get a shot at her vengeance.

"Before we begin," Gray started, "let me introduce you to Ultear daughter of Ur Milkovich. She'll be my bodyguard henceforth, all questions regarding the matter will be addressed later."

Turning to Ultear he continued, "These are people I trust with my life and the nation's future. You've met Erza, my general —" Erza nodded towards her curtly.

"Next to her is Jellal, his birds whisper to him from across the known land —" Jellal offered her a polite smile that didn't fool her in the least.

"Gajeel is our weapons expert —" which was obvious to her, considering his interest was more towards the blade on her hip, than her face.

"Porlyusica is our chief medical supervisor, and Wendy her protégé," the old lady didn't bother acknowledging Ultear, but Wendy offered her a polite bow.

"Natsu is our ammunitions guy…somehow."

"Hey!" Responded Natsu, before offering her a genuinely friendly wave.

"And Lucy is my right-hand woman. Her brains are probably how we've made it here so far."

"Heartfilia?" Ultear asked out of the blue, interrupting Lucy's greeting and startling everyone with her first actual response.

"Y-yes?" She replied. "Have we met before?"

Ultear took a moment to relive a small memory from her past, of a kind woman who helped her when she was lost in the old capital.

"You look so much like your mother," she stated, by way of explanation.

She didn't miss Lucy's sad smile, or the group's cautious glances in her direction. "Thank you," she said softly. Honestly.

Ultear felt the urge to somehow make her feel better — this person who had clearly been through pain so much like her own. So it relieved her to see the man named Natsu gently hold her hand, squeezing it.

The look they shared felt too warm, too pure for the war time setting.

The clearing of a throat brought everyone's attention back to Gray.

"Back to where we were, we need to — Gajeel, I said all questions after," he groaned.

"Kinda important," said Gajeel.

Reading his tone and against his better judgement, Gray allowed him to continue.

"Are ya doing this whole new Princely act for the bodyguard woman?"

Gray lost all semblance of poise as he coughed on his own spit, turning a bright red.

In what was a remarkable comeback, he yelled, trying to drown out Natsu's sniggering, "N-no! I don't know what you're talking about."

"Gajeel, do not question the ways of the Prince, even if they're so obvious," reprimanded Erza in all seriousness, doing absolutely nothing to help Natsu's continued sniggering.

"We — ahem — we need to get back to the task at hand. Lucy, you want to go first?"

Nodding, Lucy stepped up and offered her strategy for the next couple of weeks. Ultear listened carefully, despite her more than healthy scepticism regarding the group and their endeavours. But if this was how she was to avenge her mother, then so be it. She might just get a crack at killing _both_ her mother's murderers, and win back the nation.

The thought had her more excited than it should have.

* * *

The days that came after were the most eventful in Ultear's life.

And that was really saying something.

The group had successfully split, moved and reunited three times, allowing for stealthier progress and better reconnaissance.

Ultear had now first-hand experience of the rag-tag army's strongest weapon — their camaraderie and sheer indomitable will. And as much as she fought it, she found herself swayed by them.

By the metal giant who had a weakness for cats. The general who couldn't help but sample any and all dresses she could. The totally-in-love-but-not-willing-to-admit-it dorks who seemed to both flirt and be completely ignorant about it at the same time. The little girl who tried so hard.

They were so obviously a family, it hurt to be among them. She knew they were all here, together, for him.

And she knew what was his value in _her_ life.

She knew she was going to hurt all these people.

It was that knowledge that had her avoid interacting with any of them as far as possible. She dodged when Erza invited her to spar, gave apologetic smiles when Lucy offered her books or Wendy became friendly. And while Natsu's random conversations weren't the kind you could avoid, she did do her best to hide her amusement and seem as disinterested as possible.

Truly the only time she could come close to being herself was when she was alone with Gray. Since their agreement, he had been calm and courteous towards her — which was admirable (she would begrudgingly admit to her herself) considering she was planning on killing him after all. She could, at times, read the guilt that lead him to behave in that manner, but she was certain she could not spare him any sympathy.

Except for the one time he wasn't all that collected.

It had been an exceedingly difficult day. Their cover had been blown, but to a family that supported their endeavours, who offered the Prince, Ultear, Erza and Wendy shelter for the night. They had almost nothing to give, but went out of their way to be as hospitable as they could. It was a quiet evening, full of positivity and warmth.

Punctured by the empty chair, the untouched toys and the dusty little shoes. No one mentioned them, but everyone noticed.

That night, Ultear followed Gray out of the little house, to the lake nearby.

And she saw him cry.

It startled her when his knees buckled, and he buried his face into his hands – hardly holding back his sobs, his entire frame wracking from the effort.

For the first time she found herself truly feeling for him. Immediately angry at herself for the sympathy, she did the first thing that came to her.

"Do _you_ really get to cry?"

And regretted it immediately.

Gray turned around to look at her, tears streaming down his face, jet black hair an absolute mess. His eyes colder that she had ever seen it.

It scared her to not see the hope that usually lit them.

"Can you just leave me alone?" He begged. _Begged_.

Shutting her up immediately.

But she didn't move either, genuine concern keeping her where she was.

He didn't seem to like that.

"Look, I know what I've done, and you'll get what you want. You will get to kill me, so could I please have a few goddamn minutesto myself?Without you breathing down my neck?"

She had no response, but to turn around and honour his wish.

Not realising how the sobs she could hear would haunt her for the rest of her life.

* * *

It didn't take him very long to notice the sudden space he was getting from his "bodyguard".

What made things worse was knowing why. It put him off to have been rendered so vulnerable in the first place, but of all people it had to be _her_ to witness it.

It took Gray every ounce of self-control to not groan out loud or bury his face in his palm at the thought.

It was easier, they didn't need more animosity while making their way to what was going to be the most crucial battle they were about to fight, but he hated the pity he could feel oozing off of her. How pathetic did you have to be to have your own would be assassin pity you?

Every now and again he would look over his shoulder, and catch her averting her eyes off him, something she never quite did before. What's more she also seemed to be a lot friendlier with Wendy, the two enjoying quiet conversations with each other as the little girl helped Ultear learn of the adventures that had led them up to meeting them. Erza was still very obviously on guard around her, but not to the extent that she had been before.

Gray wasn't sure what to feel about that, and decided to ignore it and the pity in favour of focusing on their mission. They were too close to the castle, too close to winning back his kingdom for him to get distracted over her.

Though he couldn't quite stop keeping an eye on her either. Especially since she seemed capable of such warmth and compassion to people who weren't him.

A week later, the entire team had re-congregated mere hours outside Crescent Blades castle. His home.

Everyone from Lucy to old lady Porlyusica were there and the tension was palpable in every tent, with every word and in every mind. There was every possibility of the people around them not being around by the next day.

Which is why he knew he needed to speak with her.

It did surprise him when she joined him quietly the night before the raid, no protest, glare or snarky comeback to his request to speak with her.

They sat under the stars, and the calm there made it almost hard to believe they were going to be a part of this huge battle for an entire nation's destiny in mere hours.

"I know I asked you to be by my side," Gray began, cutting straight to the chase. "But you don't have to tomorrow."

He felt her stiffen beside her.

"It's got nothing to do with my promise," he explained in a rush, but still avoiding her sharp gaze, "It's just that…you don't have to put everything on the line tomorrow."

Ultear didn't respond. Not for a while. If it hadn't been for her breathing, Gray would have had to double check to see if she was still seated next to him. Not that he was going to meet her gaze or anyth–

"Tell me about my mother."

Cold. Clinical. But he would be lying if he said he didn't detect the small hint of curiosity, of hope.

He turned to find her looking right at him, eyes just as honest, as revealing.

He took a deep breath from between his teeth. "She was my teacher, and I wouldn't be wielding my sword the way I do if it weren't for her…you know that."

She stayed silent, but nodded her wish for him to continue.

"While Father was out fighting wars and Mother was at court, it was she who took care of me. She was brave, strong, kind and everything I would hope to be when I grew up. She always believed in me, and believed that I could be a good, just King to my people. She had a fun side too though, always slipping me sweets even after Mother said no."

"Why did she leave me then?"

It was the softest her voice had ever been, enough to jar Gray out of his fond memories, guilt resurfacing.

"To keep you safe. She knew what she was getting into, but that was the best way she could think of at the time. She never stopped missing you though," he added softly, thinking of all the times she would talk about her precious daughter, or cry when she thought he wasn't looking.

"Safe?" Ultear chuckled dryly, the sound painful for Gray to hear. He wasn't sure if he had any right to ask, and so he didn't. He didn't even reach out to her, knowing it wouldn't have been appreciated in the least.

Yet, it was the most they had talked since meeting each other, and Gray was grateful for it, for getting to be a little more to Ur's precious daughter than just a target.

"A-and what happened that night?" she asked finally, coldness seeping back into her voice, but just so.

Gray unconsciously clenched his fist, a familiar rage rising inside him yet again.

"I was overconfident. After I saw Mother's body, I charged. Blindly." Gray spoke through gritted teeth, eyes squeezing shut against the memory. "She came in just as I was about to lose my head. She and Lady Layla held Deliora off until I could escape."

 _'Live, Gray! **You** are this nation's future.'_

"They died protecting me."

It took a while, but Gray fought down the myriad of emotions threatening to engulf him. He hadn't had to explicitly mention any of this before, and it was more taxing than he had imagined.

He couldn't bring himself to say what he wanted to most, however. Gray knew all too well that any apology coming from him would sound hollow no matter how much raw emotion he poured into it.

Not when she silently stood up, not bothering to wipe her tears. Not when she turned around and began walking away.

This wasn't about him and his feelings anyway. It was for the mentor who died in his stead, and for her daughter who had to grow up not knowing her.

He hoped his head would soothe some of that pain.

 _'As if Deliora's would soothe yours?'_

"I will fight tomorrow. This is my country as well," she said finally, leaving the Prince alone, gazing into the night.

And for the first time in a long while, he found himself praying.

* * *

Gray rested his weight on his sword, panting as he grounded himself from the latest wave of dizziness hitting him. He could feel the toll of the blood loss, his battle-trained body screaming in pain.

But his focus was set on the person in front of him, grinning manically back. The creep, the _demon_ , was actually enjoying this.

The offensive had worked in catching Deliora's troops by surprise, mostly thanks to those in the army still loyal to the exiled prince. He had had to part with almost everyone along the way to the throne room, each fighting member standing by to hold back those after his life, buying time to do what had to be done.

Too many people were relying on him to get this right, and get out of it alive, and Gray had absolutely no intention of letting them down.

But the sheer difference between experience showed in the blood running down Gray's face and sides that had him limping and panting, versus the mild inconvenience Deliora's wounds seemed to be causing him.

Gray put his weight back on his feet and squared his shoulders once more. He had long since tuned out Deliora's taunts, choosing to grieve over the gory details in them when he could afford to. For now, he had to stay alive.

And kill him.

Putting all the effort he could muster, Gray charged at the older man, aiming for the one wound on his body that seemed to be giving Deliora most trouble – on his left side.

He was so focused on that one spot, he didn't see the attack aimed at his heart, not until the last second.

Not until he was pushed, and found another standing where he should have been.

The sight terrified him, seeing the curly weapon slice so easily through Ultear, who only moments ago seemed to have lost consciousness. But with Deliora's sword caught in her left shoulder, he had the perfect opening to slice his through the demon. This, along with a well-placed simultaneous stab from Ultear right through the demon's neck, sealed their victory.

Watching him fall made Gray feel nothing, his immediate attention drawn back to the kneeling, bleeding Ultear.

He wanted to yell at her, tell her off for how stupid a move it had been to stand between him and the sword, but he had no energy.

Not even to reach closer to her as she collapsed.

He barely felt his own tears streaming down, as he tried reaching for her, the sight of dark hair matted in blood too familiar. So as soon as he spotted Lucy enter the destroyed throne room, he spent the last of his energy asking at her to save Ultear.

Before he too, lost consciousness.

* * *

Recovery had taken a long time, for him as well as the country.

Five years later, and his nation was still rebuilding from all the damage Deliora's rule had inflicted on his country. It had been a challenge to re-establish diplomatic ties that had been severed, along with trade and strategic relations.

However, what was far more difficult, was bringing his own people back to how they used to be, considering the trauma and loss they endured in his absence. While his ascension to the throne was heralded by most, there were still far too many who saw him as too young or too incapable.

The coward who ran away.

Gray thanked every star for all the people who did have his back. From his Prime Minister Lucy – a whose sharp intellect and kind heart was one of the major reasons their nation was so close to its original global standing, to Wendy and Porlyusica whose research and effort ensured better health to more than those living in the capital.

Gajeel and Jellal who worked hard at taking out the last remaining supporters of Deliora's reign of cruelty.

Natsu and Erza – whose losses had been painful and their absence too palpable to ever really overcome. Erza's successor had successfully mobilised the army to inspire faith in people, and fear into those aiming to harm them, and Lucy would go on to ensure that Natsu was forever immortalised in legend through ink she painted his stories with.

And then there was her.

Ultear had continued to stand closely by his side over the last few years, from the time she had recovered from the battle. She now sported a prosthetic left arm, but she was rendered no less dangerous than she had been before. On the contrary, she stayed true to her post, now as Guard to the King, proving her worth on more than one occasion.

But the war had changed her as well. Gray soon learned of her steady friendship with Lucy, having been there for her, when he could not afford the time. Something he would be eternally grateful for.

She was smiling more, laughing more, and on occasion, unafraid of her own tears. She had also gone on to "adopt" an orphan, the relationship opening a new side of her Gray wouldn't have otherwise imagined existed.

He caught himself sometimes wishing some of that warmth was directed towards him.

They never spoke of his promise in those five years, though at no point was it ever off the table. He felt it every evening, when they sparred with each other.

The intent was always to kill, but not yet, and overtime he found himself wishing that some of that warmth he felt her share with others be directed at himself, no matter how unworthy of it he knew he was.

That is, until, the night he saw her wear her mother's armour.

She arrived on time to the sixth-floor balcony, and Gray took his sparring stance as usual, before he truly saw her.

And he knew.

"I don't want you to go easy on me," she said. Quietly. Surely.

Gray simply nodded, bracing himself as he watched her approach her position. Bracing himself to die at the hands of someone he had grown to care deeply for.

Watching her move in that armour, as though tailor-made for her, he took in her beauty, both inside and out.

He realised didn't want to die. He didn't want to leave his country, no matter how good a monarch Lucy would make. He didn't want to part from his friends, from his people. And worst of all, he found that he didn't want to lose the chance to get to know her better.

He realised, as she unsheathed her sword, that he had fallen for her.

And if the anguish in her eyes and the tears spilling over them were anything to go by, she may have also felt something for him.

It was visible as they fought, matching blow for painful blow, until the prince was disarmed and on his back, sword across his throat.

With nothing left in him to fight anymore, he met her gaze, before closing his eyes, surrendering himself to his promise.

"Your life is mine," she whispered.

He knew.

Especially when instead of the cold blade across his neck, he felt the gentle caress of dark hair on his face and the press of soft lips on his.

"It is," he replied softly as they parted.

She knew.

It did, in a way that had nothing to do with his promise.

* * *

 _ **A/N: Thank you so much for reading! GrayTear is my guilty ship and this took its own sweet time getting done thanks to, well, life. But it's finally up for you to enjoy.**_

 _ **Do let me know your thoughts on it! :D**_


End file.
